Penaud, 26, scored two tries and created a third with a deft chip as he moved to within three of France great Blanco's record of 38 tries for his country.
Victory ensured France topped Pool A with a perfect record of four wins from four and they will play one of Ireland, Scotland and South Africa in the last eight.
They will know their opponents after the Irish take on the Scots at the Stade de France in Paris on Saturday. This was not quite the unstoppable try-fest New Zealand inflicted on Italy a week ago in a 96-17 hammering, but there was nonetheless a gulf in class between two sides that had been separated only by five points in the Six Nations in February.
Such was Penaud's brilliance, it was almost possible to forget that France captain and talisman Antoine Dupont was out injured with a fractured cheekbone, which had dominated the news in the build-up to this game.